


similarities

by maiselocked



Category: Criminal Minds (US TV), Sherlock (TV)
Genre: Brother-Sister Relationships, Chaptered, F/M, Holmes Brothers, Mycroft Being Mycroft, Mycroft Being a Good Brother, Oblivious Spencer Reid, Protective Big Brother Mycroft, Sherlock Being Sherlock, Soft Spencer Reid, Spencer Reid is flustered, sherlock's twin sister
Language: English
Status: Completed
Published: 2020-05-29
Updated: 2021-01-07
Packaged: 2021-03-02 23:14:24
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 4
Words: 3,793
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24434926
Author URL: https://archiveofourown.org/users/maiselocked/pseuds/maiselocked
Summary: DISCONTINUED being rewritten under the same name, check my account for it!!in which the yourself and your brothers travel to quantico to help the bau with their puzzling case.(sherlock's twin sister!reader)(spencer reid x reader)
Relationships: Spencer Reid/Reader, Spencer Reid/You
Comments: 11
Kudos: 139





	1. the flight

**Author's Note:**

> this is the first crossover i have ever done!!! ever!!!! but once i got this idea in my head, it wouldn't go away, hence why i gave in and decided to write it.

You were having a peaceful day. Emphasis on _were_. Sherlock had no cases, John was out with Rosie visiting family, and you were on the couch in 221B, reading your favorite book. It was so nice having nothing to do and allowing your already active mind rest for a while. And then those all too familiar footsteps came bounding up the stairs with a softer, but just as powerful pair followed behind them. 

With a loud sigh, you closed the book after marking the page and prepared yourself to have piles of information about a case dumped on you at once. 

“Y/N!” Sherlock, your twin brother, called out when he entered the flat. He looked around until he spotted you resting on the couch. “Y/N.”

“Yes, brother?” You responded casually. Mycroft came in only a few seconds after, umbrella held in his hand as it always was. “Brothers?” 

“Free your schedule for next week. Maybe the next one as well. It depends on how quick we can work,” Sherlock declared. 

“What? Why?” You questioned, standing up from the couch. 

“We’re going to Quantico, Virginia,” Mycroft explained as Sherlock bounced around the apartment in search of some suitcases and duffel bags. 

“Quantico? Isn’t that where the FBI Academy is?” 

Sherlock threw a duffel bag at you and your quick reflexes let you catch it with ease. “Yes. It’s where we’re going.”

“And are you going to tell me why?”

“We’ll have to explain on the plane, Y/N. Time is of the essence, dear sister,” Mycroft explained in a calmer voice than Sherlock had. The two brothers had an odd balance that seemed to work much to your confusion. “Please bag your bags as quickly as you can.” 

You quickly nodded and jogged up the stairs to your bedroom. All the while you were packing your bags with clothes and toiletries, you wondered what the FBI could possibly want with yourself and your two brothers. For a split second, you thought that maybe Sherlock had gone and done something stupid as he tends to do a lot but Mycroft wouldn’t be as calm as he was. You simply decided to focus on packing bags and in a black car heading to the airport 10 minutes later. 

\--

“So can you explain why we’re heading to Virginia? What could the FBI possibly need from us?” You asked the two. 

Mycroft handed you three manila folders that were packed with documents and pictures. He gestured for you to open and sift through them while he explained what was happening. 

“In the past two months, six serial killers have escaped from top security prisons and have seemed to form some sort of alliance. They’re all highly dangerous and have taken over thirty lives. They fear that this group may pass crossing state lines and start to migrate to other countries which makes it a security threat thus landing this folder on my desk at approximately 8:32 in the morning,” Mycroft told you. 

The details and pictures of the cases were horrifying and gory. You were sure that you could feel your previous meals trying to come up. 

“Supposedly the police forces and the FBI have done everything they can to find out how they escaped, where they are, and what they’re going to do next but they’re proving to be highly unpredictable. So, I reached out and offered our help.”

“What are we going to do?” You said, closing the folders and sitting them down then rubbing your stomach in an attempt to sooth the sickness you felt. 

Sherlock remained still but spoke up. “The two of us are highly regarded in English media and we share similar deduction skills though I fear you may be losing your speed, Y/N. Mycroft is the British Government. I feel as though that one should be self-explanatory.” 

Mycroft noticed your contorted, nauseated appearance and dug through his pockets for a packet of medicine. He politely offered them to you and you gratefully accepted, taking a bottle of water he handed to you next. Once he was sure you felt fine, Mycroft continued to brief you on what would happen once you arrived in Quantico. “We’ll be working side by side with the Behavioral Analysis Unit, or the BAU, no matter how bad any of us would prefer to work alone. If we can get this done quickly-”

“Which we will,” Sherlock interrupted. 

“-we can go back home and you can finish rereading the book you have read 15 times now, Y/N.” 

“How silly of you to think I didn’t pack it so I could continue reading,” you said with a smile, pulling the book out of your carry on bag and opening back up to the page you were on.

\--

_BAU/CM POV_

“Guys. Briefing room,” Aaron Hotchner called out to the bullpen of BAU agents in front of him. “It’s important,” he added before heading into the room. 

The agents looked at each other with slightly confused expressions but did as their boss asked. 

“Do you think they got any new information?” JJ asked, coming up to Spencer who was sucking on a red lollipop that was staining his lips and tongue. 

“I doubt it. If we got new information, Hotch wouldn’t waste the time to properly and professionally brief us. The case is too important for him to do something like that,” Spencer answered. 

The team gathered in the room, all taking their respective seats at the round table. Hotch was fiddling around with a laptop but none of them could see what he was trying to bring up. Eventually, a picture of two people who looked strikingly similar, both wearing black overcoats, the collars tilted up in an effort to hide their faces from cameras. 

Another picture came up beside that one, this time an older man with an appearance that matched the other two. He was dressed in a professional suit and seated at a large desk. Spencer’s sharp eyes looked at the unknown people on the screen and figured that the resemblance wasn’t a coincidence and the three people were all related. His gaze, though, seemed to linger on the woman in the first photograph. He committed her face to memory before giving his attention to Hotch. 

“Due to the extremity of this case and the very possible threat to other countries, we’ve attracted the attention of England national security. Particularly the MI6 and one of their higher-ups, Mycroft Holmes,” Hotch gestured to the older man in the suit when he said the name. “He’s offered his own personal help along with the help of his two younger siblings, Sherlock and Y/N Holmes.”

The agents in front of Hotch followed his gestures to each person on the screen, soaking up the information. “What can three random British people possibly do to help this case?” Morgan spoke up, completely confused by the concept. 

Hotch took a breath and pulled up _multiple_ articles, news clippings, videos, and reports all of which praised the intelligent minds of the Holmes siblings. “Sherlock and Y/N Holmes run a sort of private investigation and consultation business that has time and time again solved some of the hardest, most unsolvable cases. They’re credited as being ‘masters of deduction’,” Hotch said, placing air quotes around the phrase. 

“So they’re like us just private? I still don’t see the significance.”

“Well actually, deduction is quite different from profiling. Whereas we’re able to define an unsub based on crime scenes and victimology, deduction is the ability to pull the tiniest to most important details of a person or situation from a simple observation. Those who are credited with the skill of deduction tend to have hyperactive, busy minds,” Spencer explained, finishing off his explanation with a loud crunch to his lollipop. 

“I’ve done some of my own research into the Holmes family and they could be a very valuable asset to our investigation. And if they aren’t, at least it was worth a try,” Hotch said. 

“You are correct,” a voice drew the attention away from Hotch and to the door. “We are and will be a very valuable asset.”

Standing in the doorway were the three people who were still on the large screen in the room. Everyone in the room stood, ready to give introductions and welcome the family. Spencer was standing behind JJ though his tall frame was still visible above her. He looked over the two men before focusing all of his attention on the woman who stood in the middle of the two. 

Reid could’ve passed out from the wave of nervousness that suddenly took him over. The photograph didn’t do your looks justice, he thought. At that moment, he could’ve swore he had butterflies flying all throughout his body and they only amplified when he heard your voice.

“I’m Y/N Holmes.”


	2. deductions

“I’m Y/N Holmes.” 

“Welcome,” Hotch said, extending a hand out to the three of you. You accepted the handshake out of politeness but were able to make quick deductions while doing so. Hotch reached his hand out to Mycroft and then Sherlock but neither accepted. 

“You’ll have to excuse my brothers. They’re not as accepting to touch and polite as I am,” you apologized. 

“Hey!” Sherlock defended. 

“What? It’s not a lie. You’re a dick sometimes,” you muttered. Sherlock looked to his brother for some sort of support but Mycroft only shrugged. 

“I have to agree with Y/N. You can be a dick sometimes.” 

The BAU watched as you bickered for a few minutes until you stepped in. “Boys!” You gave an apologetic glance at everyone watching at you. “Sorry about that. Shall we begin?”

Hotch went to work on pulling up photos and evidence on the screen while the rest of the team handed out some papers to you and your brothers. One look at the two of them and you knew they were analyzing and observing every person in the room as they always do. You knew they figured that JJ was a mother of two sons, Hotch had a son but was a widower, and that Spencer had been formerly addicted to some sort of pain medication. 

Spencer Reid. You could feel his eyes on you from the moment you walked in the room and surely he could feel your eyes on him. The glances Spencer gave you didn’t go unnoticed by Morgan whose smug smile grew every passing second. 

He slapped a hand on Spencer’s shoulder which made the doctor jump. “You find her pretty, don’t you?” 

Spencer looked at Morgan in disbelief. “What? Who? No, I don’t,” he stuttered out. 

Morgan barked out a laugh. “She _is_ pretty. Why don’t you go talk to her? She’s not doing anything,” he suggested, not-so-subtly pushing him towards you. You looked away from your brothers and to the two men who were coming towards you. “Hi, I’m Derek Morgan,” the man pushing the other said with a hand extended. 

You took the hand and shook it with a grateful smile. “Y/N Holmes.”

“And pretty boy here is Dr. Spencer Reid,” he added. Spencer was too flustered to greet you until Morgan nudged his side. It seemed to shake him out of his trance and he shook your hand. 

You jumped at a sudden touch on your back and when you looked over your shoulder, Sherlock was standing there, a serious look on his face. “Introduce me, Y/N,” he declared. 

“Spencer, Derek, this is my twin brother, Sherlock. Sherlock, this is Dr. Reid and Agent Derek Morgan.” 

“Nice to meet you,” Sherlock said but you knew he didn’t mean it. You knew he had figured everything out about them. He couldn’t turn off the emotionless deduction like you could.

“Okay, let’s get started,” Hotch called from the front of the room, bringing everyone’s attention to the screen. Pictures of the bodies and scenes were plastered across the screen and your sharp eyes scanned every detail. You tuned out the words of Hotch and anyone else who had been speaking. 

_Sedentary lifestyle. Office worker._

_No individuality. Blends in._

_Personal crime. Killer knew the victim._

_Two cats. Scratches all over arms prior to death._

_Grew up in an average family._

_Public university. Not rich._

When you refocused your attention on Hotch, he had just finished speaking and was looking at the three of you expectantly. When you realized your brothers were still focused on Sherlock was likely slipping into his mind palace, you spoke up. 

“Can I see the bodies in person? I have more medical and forensic experience,” you told them. 

“They’ve already had autopsies performed,” Hotch answered. 

“They miss things. They always do. Trust me. I won’t miss anything,” you said confidently. 

“How can you be so sure?” Emily Prentiss asked out of skepticism. 

“I have solved hundreds of crimes with my brother and one hundred and four by myself. I graduated from Cambridge with three degrees. I have experience in this. The medical examiners and forensic scientists will _always_ look over the most important details that seem insignificant to them. They see but they don’t analyze.” 

Emily held up her hands in surrender and leaned back in her chair. A wave of satisfaction came over you and you looked back at Hotch with waiting eyes. “Reid, take Y/N to the medical examiner’s office,” he said. 

“Mycroft and I will look at the crime scenes. Preferably alone,” Sherlock said, coming out of his own mind. 

You rolled your eyes and looked at Spencer, trying to get him to leave so you don’t have to hear the argument that would soon break out between your brothers and the BAU. Spencer picked up the message and grabbed his coat, walking out of the room with you. You walked in silence for a bit until Spencer finally found the confidence to start a conversation. 

“Cambridge? That’s impressive. What’d you major in?” He asked you. He watched as you picked at your nails, a habit that came from anxiety he figured. 

“Biology, chemistry, and social sciences but I have some minors and certificates in cellular and molecular biology, linguistics, and classics.” 

Spencer’s eyebrows raised in surprise. He had his fair share of degrees and PhDs from a wide range of schools but he felt almost intimidated. Even though he was intimidated, it was a little refreshing to be with someone who would understand his explanations, nerdy jokes, and obsessions with classic literature. 

“So, Dr. Spencer Reid, tell me about yourself.”

The two of you reached the parking garage of the building and Spencer led you over to a car and unlocked the doors. When you got in, he turned the engine and pulled out.

“There’s not much about me to talk about,” he said with pure honesty but you knew that was bullshit. 

“That’s a lie. You seem interesting and I want to learn more about you.”

“You can deduce everything about a person so why are you asking me about myself?” 

“Well, I can tell which side of the bed you sleep on, your previous ailments, the gel you use in your hair, your dominant hand, your far from usual childhood, your family history of schizophrenia but I want to know what your favorite book is, what music you listen to, what shows you watch. I can’t deduce that.”

Spencer smiled, the faintest blush coming to his cheeks. The corners of your lips tilted up in a small smile. _Damn, he’s really cute…...Shit._


	3. medical examiner

“I don’t understand. The autopsies have been performed. All bodies are set to be removed and buried properly tomorrow.”

You rolled your eyes at the medical examiner denying you entrance into the morgue. “I would like to take a last look at all of them before they’re removed. It’s simply detrimental to the case,” you told him. 

“I’ve been given orders to not take them out or allow anyone else to look. I’m sorry, Ms. Holmes.” 

Spencer watched the interaction a few feet behind you, hands clutching onto his messenger bag. He wasn’t a wuss or a coward but by now he would’ve left and had Hotch call the medical examiner's office. In a way, he admired your dedication. 

“Screw this,” you muttered and made an attempt to push past the man but he placed both of his hands on your shoulders and pushed you back. An airy chuckle came out of you and you gave him one of the strongest glares you could muster. _Boy, if looks could kill...._ , Spencer thought to himself. 

The doctor seemed to immediately regret his actions as he noticed your hand had formed into a fist. “Normally I would be a lot harsher with someone who not only put their hands on me but _pushed_ me but I’m in a good mood right now so I’m just going to give you a small warning,” you paused to read his name tag, “Dr. Warner. The next time you even think about placing your hands on me, I won’t be the only one hurting you. No, see, I have _several_ people in my phone who would do far worse than I for putting your hands on me. Two of which are here in Quantico. Now, I suggest you let me in that _goddamn_ lab before I tell them your hands went a little further south than they really did.”

Dr. Warner’s face seemed to pale and with slight shaky hands, he led you and Spencer to the door of the lab. Spencer would be lying if he said that wasn’t the moment he realized that he had a crush on you. 

The three of you stepped into the lab, the very strong smell of bodies and disinfectant not bothering you at all. You pulled out the magnifying glasses Mycroft had gifted you a year back and positioned them on the bridge of your nose. Spencer watched with curiosity as you moved around the room like you owned it, slipping gloves on your hands and a mask over your mouth. The smallest smirk came to his face as he began to replicate your movements as Dr. Warner laid one of the bodies on the table. 

As soon as it hit the cold metal, your eyes began scanning. You gently lifted the victims wrists in search of signs of being bound but found no evidence of it. 

“Where are the other bodies?” You asked, wondering if they had been buried and if so, if they could be exhumed. 

“They’ve already been buried. These three are the only victims within the past week.” 

“But we’ve gathered that they kill about five a week. So either they have two hostage, two bodies hidden well, or they’re killing at this very moment.” 

“Why do they have to follow a schedule? I mean, they’re serial killers. I don’t think they have some clipboard on a wall that their boss fills out every monday.” 

You were about to retaliate rather sharply but Spencer spoke up before you could. “They’ve been at this for two months. Two months and they’ve never divvied off schedule. It’s quite likely they have some sort of leader that may have a superiority complex mixed with a need to be completely organized in every one of their affairs. Y/N is right.” 

A smug smile came to your face and you held out your fist to Spencer as an invitation for a fist bump. He gave you the same smile and gave you a small fist bump. 

Your mind seemed to be in two places as you made an attempt to deduce anything you could about the body in front of you. It was hard to slip into your own make-shift “mind palace” as Sherlock so ridiculously coined it as Spencer’s eyes were seemingly staring into your soul. 

You decided to let your mind wander for just a split second. Spencer was sweet, he was nice, and had an intelligence level that matched your own. It was refreshing to be with someone who was able to keep up with your speed-

“Ah-ha!” You exclaimed, spotting the smallest, almost undetectable prick in the body's skin right at her hairline. “Told you I’d catch things. Nobody ever believes me. Is it because I’m a girl? Do I not have high enough cheekbones to come off just as pretentious and intelligent as Sherlock? Am I not as smart because I don’t wear waistcoats and carry around a fucking umbrella sword everywhere?” 

Spencer figured it was smart not to answer any of your questions but he had to hold back a few laughs as you kept making small remarks about your brothers. 

“Spencer.” 

“Yes?” He looked up at you with curious eyes.

“Humor me for a moment. You’re the killer. I’m your victim. Obviously I am resisting and fighting you off. Look at these defensive marks. You know that I would fight you. You know most people would fight you. You’ve killed before. You’re in a group with five other killers. They know this too. But I have no marks of ropes or wires or tape. So how could you essentially paralyze me before you ruthlessly kill me?” 

“Drug you.” 

Dr. Warner watched with crossed arms. “But any drug would’ve been detected in the toxicological test,” he says.

“No, see, the killer is smart. He has biological knowledge, pharmaceutical knowledge. He knows what will show up and won’t. I need you to test this body and the other three again but extensively. Paralytics like Vecuromium or Succinylcholine are metabolized so quickly that it's not detectable in any scans. You'd have to test them individually. Take the blood samples from the past victims and test them as well. Call when the results are in.” 

You tore the gloves off of your hands and folded your glasses back into your pocket. “Come on, Spence.” 

Spencer followed you out of the lab as you called your brother and told him the news while also making sure he hadn’t made anyone want to kill him. Butterflies filled his stomach at the sound of “Spence” in your thick British accent. God, he felt like such a highschooler.

**Notes for the Chapter:**

> this chapter sucks just a little. i'm not a medical examiner or a scientist nor can i deduce anything. i apologize for any inaccuracies. also i don't know paralyzing agents that don't show up in toxicology reports ??? so i'm very sorry for that


	4. UPDATE

**Summary for the Chapter:**

> just an update about this story :)

hi!! so i started this story a few months ago and i haven't updated it in a long time because i genuinely hated how i wrote it and started it. but i really love the plot and i love the crossover and the story in general so i decided to rewrite it completely on a new post. it's by the same title and i'm going to add the link here. thank you so much for enjoying the story and i hope it'll be better this time around <3

https://archiveofourown.org/works/28602342/chapters/70101456


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